Process and apparatus for making wrapped yarns



Feb. 6, 1968 F. c. FIELD, JR 3,367,095

PROCESS AND APPARATUS FOR MAKING WRAPPED YARNS Filed June 30, 1967 2 Sheets-Sheet 1 INVENTOR 54 FREDERICK C. FIELD, JR.

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ATTORNEY Feb. 6, 1968 F. c. FIELD, JR 3,357,095

PROCESS AND APPARATUS FOR MAKING WRAPPED YARNS Filed June 30, 1967 2 Sheets-Sheet INVENTOR FREDERICK C. FIELD, JR.

MZMM ATTORNEY United States Patent 3,367,095 PRUCEES AND APPARATUS F012 MAKING WRAPPED YARNS Frederick C. yield, J12, Wiimington, DeL, assignor to E. 1. tin Pont de Nemonrs and Company, Wilmington, Del., a corporation of Delaware (:ontinnation-impart of application Ser. No. 397,139, Sept. fl, 1964. This application June 30, 1967, Ser. No. 656 437 5 Ciairns. (Cl. 57-5) ABSTRACT 0F THE DISCLGSURE A method and apparatus are disclosed for combining discontinuous fibers and two or more continuous core elements to form a yarn having a surface wrapping of O fibers twisted about substantially straight core elements with portions of surface fibers locked into place in the core. A stream of separated discontinuous fibers, supplied by drafting sliver or other source of fibers, is fed into a chamber. The fibers are forwarded through the chamber 5 in a compressible fluid stream so that the individual fibers are supported by the stream. Separate, continuous multifilament core elements are fed into a chamber to converge with each other and the stream-supported fibers and then pass from the chamber through a false twisting device. The core elements are false twisted together to cause twist to back up into the chamber and combine the fibers with the core elements. During travel beyond the false twisting device, the twist is removed from the core elements and the fibers are reverse-twisted about the core elements to form a surface wrapping which holds the core together as a compact bundle.

Cross-reference to related application This is a continuation-in-part of my application Ser. No. 397,139, filed Sept. 17, 1964, wherein restriction was required between the present invention and the wrapped core yarn claimed therein.

Specification 359N Patented Feb. 6, 168

The novel wrapped yarn provided by this invention is an improvement over yarn prepared in accordance with my US. Patent No. 3,079,746 of Mar. 5, 1963. The yarns are similar in having surface wrappings of discontinuous textile fibers tightly twisted about a core of relatively straight textile fibers, the core fibers being held together as a compact bundle by the wrappings. There is a predominance of true twist in the wrappings and the core may be substantially free from true twist. However, the yarn produced by the present process is further characterized by having a core of at least two continuous, integral core elements, such as multifilament textile yarns composed of continuous or discontinuous fibers, and by having portions of surface fibers locked in place in-between the core elements, in a manner which holds the surface wrappings in position. The individual core elements may be twisted or free from twist, but there is substantially no twist of the core elements about each other unless twist is introduced in subsequent processing of the yarn product. Preferably the improved yarn is also characterized by the surface fibers being helically twisted tightly about the bundle of core filaments such that the twist level of said surface fibers is relatively constant along the length of the yarn.

The invention provides a novel twist transference, fluid twisting process for producing the yarn which is an improvement over the process described and claimed in my US. Patent No. 3,079,746 of Mar. 5, 1963. This improved process involves bringing together, at a convergence point upstream from a false-twisting device, discontinuous fibers and two or more separate, continuous, integral core elements, and twisting the discontinuous fibers about the core elements downstream from the false twisting device to form the novel yarn. A further aspect of this invention is a suitable apparatus for making the above-mentioned improved yarn which comprises, in combination, a falsetwisting means, means providing a convergence point upstream from said false-twisting means, means for feeding separate core elements to said convergence point, and separate means for pneumatically feeding discontinuous textile fibers to said convergence point, which may or may not require means for drafting said discontinuous fibers prior to contact with said core elements.

The invention will be more fully understood by reference to the accompanying drawings in which:

FIGURE 1 is a schematic representation of a specific embodiment of the process and apparatus for producing the novel yarn of this invention;

FIGURE 2 illustrates a wrapped yarn product of this invention on an enlarged scale;

FIGURE 3 is a greatly enlarged cross-sectional view of a wrapped yarn product of this invention, illustrating that discontinuous fibers are locked in place between core filaments, the ends of which are shown as circles, and are also Wrapped around the bundle of core filaments; and

FIGURE 4 is a schematic representation of another embodiment of the process and apparatus of this invention.

In FIGURE 1, a large number of fibers or slivers it), from a suitable source, are fed in side-by-side relationship between back rolls l2 and 14 of a conventional spinning frame, pass between a pair of control rolls 16 and 18, and between guide rolls 20 and 22 to the front drafting rolls 24 and 26 of the frame. Passing about the control and to guide rolls are a pair of aprons 28 and 30, which support and assist in drafting the slivers. The relative speeds of the above sets of rolls are controlled in conventional manner for normal drafting of slivers, which is usually in the range from about 20X to lOOX.

The front rolls 24, 26 feed the drafted slivers to the novel treatment of this invention as a stream of discontinuous fibers, which may be a loose mass of fibers in the form of a sheet or bundle, as illustrated, or other forms equivalent for the purpose. The fibers pass directly into the back end of treating chamber 32 and are borne forward in a current of air. The air current is created by suction through duct 34, which opens into the chamber near the forward end. It may be desirable to place a screen over the duct Opening to prevent removal of short fibers, but this is not necessary with usual staple lengths. Also, although a screen is sometimes useful to separate short fibers from the exiting air stream, very short fibers tend to catch in the screen and not be picked up in the yarn being produced.

Continuous core elements 36 are fed separately into chamber 32 through opposed openings 33 located in-' termediate the back and front ends. Two core elements are shown entering the chamber through a pair of openings, but a larger number may be used to provide modified products. Also, the front rolls 24, 26 are shown controlling the feed rate of the core elements, but separate feed rolls can be used to deliver these elements at a higher or lower speed than the front rolls would provide. The continuous core elements and the airborne fibers are combined into a single strand 46 which exits from the chamber through an opening 42 in the front end. The chamber is open at the back end to receive the fibers from the front rolls and is otherwise completely enclosed except for the additional openings mentioned above. The flattened box-like chamber shown has been found highly effective for the purpose of this invention, but other shapes can obviously be used to cause the fibers to be transported in a suitable airborne condition for combination with the continuous core elements.

The strand 40 of combined core elements and fibers, exiting from opening 42 of the box, passes through a false-twisting device 44 to windup roll 46 which is surface driven by roll 48 to maintain the strand under uniform tension. A variety of windups or other yarn-collecting devices can be used. Device 44 is preferably a torque jet but may be any of the known false twisters for introducing twist which backs up along the strand, as it travels toward the device, to a point within the chamber 32 where the continuous core elements converge and are twisted together. The airborne fibers are randomly caught up by the twisting core elements and receive a lesser twist. Hence the strand passing to the false twister has a high degree of twist of the core elements about each other, and lesser amounts of twist of the fibers about the core. The core twist is substantially all removed as the strand travels on beyond the false twister to the take-up rolls. The less highly-twisted surface fibers first untwist and then twist in reverse direction as untwisting of the core elements takes place. This phenomenum will be referred to as twist transference. The result is that the product has fibers twisted tightly about substantially straight core elements as illustrated in FIGURE 2.

The yarn illustrated on an enlarged scale in FIGURE 2 has staple fibers Si) helically twisted about core elements composed of substantially straight continuous filaments S2. The major proportion of the fibers are wrapped tightly about the core in helical bands which resemble stripes on a barbers pole. There are also a number of projecting fiber loops 54 and loose fiber ends 56. In other embodiments which have a larger proportion of fibers relative to the core elements, there may be a substantially continuous surface wrapping of fibers on the yarn core.

FIGURE 3 shows the appearance of a greatly enlarged cross-section of the above yarn. In addition to the major proportion of staple fibers 50, wrapped around the core bundle of continuous filaments 52, a minor proportion of staple fiber ends 58 are seen between some of the filaments 52 in the core. This embodiment is made with a pair of core elements, and fiber ends 58 lie between the juncture of the two elements. Fibers having portions locked in place in the core, in this manner, are present in surface wrappings and hold the wrappings in place. In this embodiment, the discontinuous fibers have been shown as having flattened cross sections so that the ends 59 and 58 are readily distinguishable from the filaments 52 of circular cross section.

FIGURE 4 illustrates a modified process and apparatus in which six carrier yarns converge with each other and the airborne discontinuous fibers and become core elements in the wrapped yarn. Two ends of sliver, 9 and 10, are shown being fed to a conventional spinning frame, the parts of which are numbered to correspond to the similar frame of FIGURE 1. In this embodiment, the treating chamber consists of two parts, a transfer duct 32 and a convergence duct 33. The duct 33 connects the transfer duct to a suction duct 34, which creates an air current through both chambers. A stream of separated fibers 31 is fed by rolls 24, 26 into transfer duct 32, the fibers become airborne and are converged in duct 33. Carrier yarns 36 are fed at any desired speed by independent feed rolls 35, 37 (which may have different speeds) and converge with each other and the airborne fibers after passing through openings 38 in convergence duct 33. The yarns are guided to the duct through eyelet board 39. The yarns pick up the fibers and are twisted together by torque jet 44 to form a strand 4%, which passes through the torque jet to letdown rolls 43, 45 and windup 46, 48. Twist is removed from the yarn core during travel away from the torque jet, and twist transference causes surface fibers to twist tightly about the core.

More than one core element may be fed through each opening 38 providing there are at least two separate openings feeding continuous core elements. Any collection devicec may be employedv after the yarn passes through any tension maintaining and forwarding device downstream of the torque jet. The torque jet itself could serve to maintain tension and advance the filaments if it is made to aspirate.

Suitable raw materials for making the yarns of this invention include all synthetic and nature fibers and filaments, and combinations thereof. The filaments or fibers of the continuous core elements and the discontinuous fibers having free ends which form the wrapping elements may have the same or different cross sections and may be composed of the same or different compositions. Natural fibers that may be used include cotton, wool, silk, ramie, flax, jute, hemp and the like. Regenerated fibers (e.g., rayon) and synthetic fibers may also be used. Suitable synthetic fibers include polyamides such as poly(epsilon caproamide) and poly(hexamethylene adipamide), poly- (undecanoamide) and poly(heptanoamide); cellulose esters, e.g., cellulose acetate; polyesters, particularly polyesters of terephthalic acid or isophthalic acid and a lower glycol, e.g., poly(ethylene terephthalate), poly(hexahydro-p-xylene terephthalate); polyalkylenes, e.g., polyethylene, linear polypropylene, etc.; polyvinyls and polyacrylics, e.g., polyacrylonitrile, as well as copolymers of acrylonitrile and other copolymerizable monomers (e.g., methyl methacrylate or vinyl acetate). Copolymers of ethylene terephthalate containing less than 15% combined monomers other than ethylene terephthalate an'd copolymerizable with ethylene terephthalate are also useful in practicing this invention. Also useful in the practice of this invention are spandex fibers and yarns, multi-component fibers such as described in Taylor US. Patent No. 3,038,237 and Breen U.S. Patent No. 3,038,236, as well as poly (meta-phenylene isophthalamide), and polybenzimidazole. Other compositions which are suitable for the two types of feed materials include metal fibers, glass fibers, and asbestos fibers.

The separate core elements for use in this invention are continuous bundles, with or without twist, including continuous filaments, spun yarns, monofil, mixtures of continuous filament and staple, core-spun yarns, and wrapped yarns, any of which may be plied together. The two or more core elements may be of the same composition and construction or they may be of different composition and/or ditferent construction. The discontinuous fibers which are used in making the yarn must have free ends, but may be of conventional staple length or longer. For example, the discontinuous fibers may have a length varying from one inch up to twenty inches, or even higher. They may be of the same length or of a mixture of lengths, such as is produced from a Turbo-Stapler (Turbo Machine Company, Landsale, Pa.).

The percentage of discontinuous fibers used in making the final yarn product will depend on the type of product desired and the characteristics desired in the yarn. In spinning yarns of multi-component core elements, some improvement in yarn properties can be noted when using as little as 2% to 3% of discontinuous fibers, based on the weight of final yarn product, but greater amounts are usually desirable and the products may contain up to 80% or 90% of discontinuous fibers. Preferably the amount of discontinuous fibers employed in making the wrapped yarns is less than 50%. The denier of the discontinuous fibers as well as the denier of the core elements are not critical, and will normally depend on the characteristics desired in the final yarn product. Suitable deniers may range from about 1 d.p.f. or less up to about 30 d.p.f. or even higher for certain end uses. Of the total amount of discontinuous fibers employed in making the wrapped yarns, the major proportion will be found wrapped around the surface of the multi-core yarn and only a relatively minor proportion of the discontinuous fibers will be inside the yarn product as fibers separating core elements or filaments from their neighbors.

In manufacturing the wrapped yarns, any type of falsetwisting device may be used downstream of the convergence point of discontinuous fibers with core elements, such as devices operating by mechanical means or those operating by fluid means. Suitable false-twisting devices include torque jets of the type shown in FIGURE 4 of my U.S. Patent No. 3,079,746 and fluid jets of the types illustrated in the drawings of Breen et al. U.S. Patent No. 3,009,309 of Nov. 21, 1961.

Although it is not intended to be limited by any particular theory, it is believed that, in most of the wrapped yarn products made in accordance with this invention, the discontinuous fibers appearing as wrapping elements in the surface of the yarn are in the form of a substantially continuous wrapping element running the length of the yarn. Another observation has been noted in connection with wrapped yarns of heavy denier or multi-ply, wherein the surface of the wrapped yarn exhibits a barber pole effect when the amount of discontinuous fibers in the wrapping is relatively small. As the amount of wrapping fibers is increased to larger amounts, this visual effect disappears and the discontinuous wrapping fibers completely cover the core elements throughout the length of the yarn.

In feeding the continuous core elements, on the one hand, and the discontinuous fibers on the other hand, so that these tWo feed materials meet at the stated convergence point, the relative speeds of the two feed materials may be the same or may be different. For example, the core elements may be fed to the convergence point either faster or slower than the discontinuous fiber feed. Furthermore, the feed rate of the core elements may be different from each other to produce novel effects (e.g., boucle). The convergence point of discontinuous fibers and core elements is normally set at a distance downstream of the nip of the feed rolls greater than the maximum length of discontinuous fibers, and preferably at a distance about twice the average fiber length, the 2% of longest fibers in mixture of different lengths, such as a Turbo product, being neglected in said average.

An important advantage of the present invention is that it provides a new wrapped yarn structure having a superior combination of surface stability, slippage resistance, knot holding ability, and strength over wrapped yarns made heretofore. Most of the superior properties exhibited by the novel wrapped yarns are due to the discontinuous fibers which are locked in place between continuous core elements in the interior of the new wrapped yarns. This is a structural feature not present, for example, in the yarns described in my U.S. Patent No. 3,079,- 746. The yarns of the present invention have a distinctly different yarn structure which provides yarn characteristics and properties superior to those of the previous yarns which have no discontinuous surface fibers, or have no continuous core elements, or their discontinuous surface wrappings are not locked in place between essentially parallel continuous core elements. Thus yarns may be prepared in accordance with my invention to have the feel, hand and bulk of spun yarn, while also having the strength, elongation, shrinkage and modulus of a continuous filament industrial yarn.

The following examples illustrate specific embodiments of this invention, but are not intended to limit the invention defined in the appended claims.

EXAMPLES A series of 16 different wrapped yarns was prepared using the equipment shown in FIGURE 1. Different fiber compositions were used; the nylon being polyhexamethylene adiparnide, the acrylic being an acrylonitrile polymer and the polyester an ethylene terephthalate polymer. Two or more continuous multifilament core elements were fed between the front rolls of the drafting frame at the indicated speeds in yards per minute. In Example 16, a set of core element feed rolls (not shown) were provided directly above the illustrated front rolls to deliver the core elements to the convergence box at a higher speed than the staple. The denier of each core bundle of essentially zero twist multifilament yarn (except Example 8 which is a spun yarn) is listed in the table together with the feeding speeds in yards per minute and the filament composition of the core bundle. The discontinuous fibers are composed of the indicated fiber composition and denier per fiber, and these staple fibers are fed in the form of a sliver to the back rolls of the frame and drafted from 20X to 100x during passage to the front rolls. The staple fibers are picked up from the front rolls by a vacuum line and brought into contact with the core elements en route to the convergence point, which, in turn, is set at a distance of approximately two times the average fiber length measured downstream from the nip of the front or feed rolls. The staple fibers forming the sliver in all except Examples 12 and 13 were obtained from continuous filaments which had been broken on a Turbo-Stapler machine, resulting in a distribution of fiber lengths with an average fiber length of approximately 3 inches. The nylon Staple was combed top, having an average fiber length of about 3 inches. The table indicates the weight percent of staple fiber which was used in making each yarn, based on the combined weights of the continuous elements and of the discontinuous elements in the final wrapped yarn product. The feeding speed of the sliver at the feed rolls is also given in the table. The false twisting device used in making the 16 yarn samples was a fluid jet of the type shown in FIGURE 4 of my U.S. Patent No. 3,079,746, which was operated with compressed air at about p.s.i.g. at room temperature. The wrapped yarns were guided to a surface driven windup (speed shown in the table). The yarn size is listed in terms of cotton count.

TABLE Continuous Core Elements Discontinuous Fibers Product Ex. No. of Denier Feed Percent Feed Windup Yarn Knot Bundles oi each Fiber Speed, of Total D.p.t. Fiber Speed, Speed, Size Strength,

Bundle y.p.n1. y.p.rn. y.p.m. (c.c.) lbs.

3 840 8. 6 4. 5 114 112 1. 80 2 840 11.5 4. 5 114 112 2. 62 3 840 7. 7 4. 5 115 110 1. 76 3 S40 4. 7 4. 5 115 103. 5 1.67 3 840 20. 1 4. 5 114 112 1. 57 6 840 11.5 4. 5 114 112 0.87 4 210 52. 5 4. 5 116 112 3. 4 840 20.0 4. 114 112 1. 27 2 S40 9. 1 2. 0 205 201 2. 85 6 840 11. 0 2.0 103 100 87 8 840 10. 3 2.0 103 100 62 2 840 15. 5 3. 0 154 150 2. 50 3 840 9. 1 3.0 154 150 1. 79 2 1,100 10. 0 3. 0 114 112 2. 18 v 12 840 22. 5 4. 5 Acrylic. 85 84 39 2 840 12.5 4.5 0 114 2.55

The yarn products were highly useful as industrial sequently removing the twist from the core elements and twines, especially for the machine tying of mail. The yarns of Examples 2, 9, 12, 14 and 16 were also useful for making upholstery fabrics. The yarn products listed in the table all had good surface stability and good knotholding ability. The knot retention of the yarn products was far superior to conventionally plied continuous filament yarns. The knot strength in pounds-to-break is listed for a number of the yarn products in the table. The knot strength of the wrapped yarns of Examples 2, 12 and 16 is much superior to that of a commercial cotton machine tying twine (0.7 cotton count, 14 lbs. knot strength).

The present invention provides a wide varietyof different yarn structures made from different fiber compositions. The wrapped yarns are useful for preparing a number of different types of woven, knitted, nonwoven, and tufted fabrics, for the industrial textile field as well as the apparel and home-furnishings textile fields. Products which may be made include sewing thread and wicks; also yarns for use in industrial fabrics, coated fabrics, industrial hose reinforcement, fire hose, industrial belts, conveyor belts, V-belts and webbing; yarns for cordage applications including ropes, tire cord, industrial and household cords and twines, including twine for machine tying of magazines, mail and the like, baler twine and hand twine; home furnishing uses including upholstery, carpets, draperies and towels; and specialty wrapped yarns for use as an effect thread in styling different types of fabrics, and the like.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustratilons except to the exent defined in the following claims.

I claim:

1. The twist-transference, faise twisting process for producing a wrapped yarn which comprises continuously feeding loose discontinuous fibers, forwarding and supporting the fibers in a compressible fluid stream, continuously feeding at least two separate continuous multifilament core elements to converge with each other and the stream-supported discontinuous fibers and then pass through false-twisting means, false twisting the core elements together to cause twist to back up and combine the discontinuous fibers with the core elements, and subreverse-twisting discontinuous fibers tightly about the core elements by twist transference to product a surface wrap,- ping of discontinuous fibers helically twisted about substantially straight core elements with portions of surface fibers locked into place between the core elements.

2. The process defined in claim 1 wherein the false twisting is accomplished by applying a torque with a fluid jet to produce a yarn having fibers helically twisted about the core at a relatively constant twist level along the yarn.

3. The process defined in claim 1 wherein the discontinuous fibers have a length of about 1 to 20 inches, the core elements are bundles of continuous filaments, and the discontinuous fibers constitute 2% to 50% of the total.

4. Apparatus for preparing a wrapped yarn comprising, in combination, fiber-separating means for continuously converting discontinuous fibers into a stream of loose fibers, a chamber for receiving the fibers, flow-producing means for transporting and supporting the fibers in a compressible fiuid stream through the chamber, yarnfeeding means for separately introducing at least two continuous core elements into the chamber to combine with the discontinuous fibers, false-twisting means for twisting the discontinuous fibers about the core elements, and yarn forwarding means for withdrawing the combination of fibers and core elements from the chamber through the false-twisting means under tension.

5. Apparatus as defined in claim 4 wherein the faisetwisting means is a torque jet.

References Cited UNITED STATES PATENTS 1,439,166 12/1922 ieany 57-16O 2,053,123 9/1936 Allcs 57-160 2,179,087 11/1939 Gibbons 57-144 2,311,356 2/1943 Astley 57144 2,411,559 11/1946 Sonin et a1. 117-33 2,449,595 9/1948 Ellis 57-144 X 2,902,820 9/1959 ronson et a1 57l63 3,079,746 3/1963 Field 57--51 3,164,951 1/1965 Donaldson et a1. 57-160 JOHN PETRAKES, Primary Examiner. 

